Technology

The use of various sand materials

1. Sandblasting: Sandblasting range: hardware derusting, aluminum alloy sandblasting, glass sandblasting (matte effect), plastic sandblasting (deburring), acrylic sandblasting (matte effect), PC, PS surface Treatment, resin surface treatment, casting workpiece sandblasting, zinc alloy sandblasting (rough surface), stainless steel "target=_blank> stainless steel material sandblasting, stone material sandblasting, hardware removal paint, hardware removal welding scar, shot blasting, etc. Accessories surface treatment

2. Acrylic sandblasting: If the customer requires very foggy, glass sand is generally sprayed. If the requirement is higher, white corundum can be used. If the requirement is not very foggy and has a certain transparency, glass beads must be used, and sometimes a little glass sand is added to the glass beads, so that the effect of spraying is a little bit transparent.

3. Stainless steel sandblasting: Generally, it is necessary to know what kind of panel stainless steel is. There are alloy steel shot on the polished surface, brushed surface, and the fog surface of the original plate. If roughness is required, and there is no requirement for surface smoothness, brown corundum can be selected. And white corundum, there are special requirements, need to be smooth, choose glass beads and white corundum.

4. Die castings: generally low-alloy steel to remove burrs, generally low-alloy steel can be used by shot blasting machine, cast steel shot steel balls, and steel balls and steel shot blasting. For the selection of steel grit to remove the surface dirt, it is generally possible to consider the mixed use of steel balls and steel grit. If you want to make the sandblasted aluminum parts whiter and some high-alloy steel, you should consider using high-cost stainless steel shot, steel wire cut shot "steel cut shot," if you want to save cost, consider cast steel ball and endless steel shot at 8:2 The proportions of the steel balls are mixed and used. When sandblasting and shot blasting, the steel balls are cleaned once every time they work, and more sandblasting and shot blasting can achieve a whiter effect.

5. Iron parts: Sandblasting iron parts is generally to remove "oxidation" oxide layer and rust, remove edge thorns, some will be electroplated with low alloy steel after sandblasting, and some will be painted after sandblasting, generally sprayed with brown corundum and white corundum (according to color requirements and economic cost considerations).

6. Digital: Computers, mobile phones, cameras, tablets and other metals are generally blasted with nylon sand, ceramic sand (zirconium sand) to clean the tiny burrs on the surface of the workpiece and make the surface of the workpiece smoother, eliminating the harm of burrs. Improve the grade of the workpiece. And sandblasting can make small rounded corners at the junction of the workpiece surface, making the workpiece more beautiful and more precise.

7. Carbon fiber frames (mountain bikes), semiconductors, molds, and refractory products are generally manufactured with black silicon carbide.
 

Blast Control

Many people don't know much about sandblasting. In fact, sandblasting is very simple. It is to hit the surface of the workpiece at a certain speed to form a certain roughness, thereby improving the coating adhesion and prolonging the anti-corrosion life.

1. Early control

 Before sandblasting, the rust grade of the surface of the metal structure substrate shall be evaluated according to the provisions of "Steel Surface Corrosion Grade and Rust Removal Grade before Coating". Check carefully, remove welding slag, spatter and other attachments, and clean the surface grease and soluble dirt, and properly dispose of useless welding bodies or joints.

2. Abrasive Control

 Sand for sand blasting and rust removal requires hard particles, angular, dry (water content <2%), no soil and other impurities; quartz sand is better, coarse river sand is also acceptable; at the same time, sand transportation conditions should be considered , unit price, recycling capacity and other factors; the particle size of the sand is preferably 0.5~1.5mm, it must be dried before screening, and stored in the shed or indoors. The mesh size is: coarse sieve 40~48 holes/cm2 (particle size 1.2 mm), fine sieves with 372 to 476 holes/cm2 (particle size 0.3 mm).
 After the rust removal plan is determined, the abrasive can be selected from river sand, quartz sand or a mixture of the two. In the reinforcement of Gangnan Reservoir, the pre-spraying comparison shows that the rust removal effect is best when quartz sand and river sand are mixed at a ratio of 1:1.

3. Tool Control

 During sandblasting operation, the air pressure of the air compressor is 6.0×105～6.5×105Pa, and the pressure amplitude is 0.5×105～1.0×105Pa. Generally, the air pressure of the sand barrel is 4.5×105～5.5×105Pa, not less than 4.0×105Pa. Before sandblasting, check whether the manufacturer of the pressure vessel holds a production license issued by the relevant department, whether the protective tools worn by the sandblaster, the safety belt (rope) and the oxygen supply device are safe and reliable, and whether the nozzle is worn or not. diameter increase
The nozzle should be replaced when it is 25% larger.

4. Environmental Control

In view of the sand blasting and rust removal of hydraulic metal structures is an open-air operation, in addition to paying attention to dust prevention and environmental protection during construction, it is also necessary to detect the ambient temperature, humidity and temperature of the metal surface at the construction site every day, calculate the dew point of the day, and make construction records. When the relative air humidity is greater than 85% and the metal surface temperature is lower than 3°C above the dew point, construction shall not be carried out.

5. Process control

 The compressed air used for sand blasting must be processed by cooling device and oil-water separator to ensure dryness and oil-free; oil-water separator must be cleaned regularly.
 The distance between the nozzle and the surface of the base steel should be 100-300mm, and the non-sandblasted parts should be shielded and protected before sandblasting.
 The angle between the spraying direction and the surface normal of the base steel is preferably 15° to 30°.
 After sandblasting and derusting, before proceeding to the next process, in case of rain or other conditions that cause the surface of the base steel to be wet, after the environment reaches the construction conditions, dry the surface moisture with dry compressed air before construction. Sandblasting, do not reduce the abrasive requirements, so as not to reduce the roughness.
 When sandblasting, the nozzle should not stay in one place for a long time. The sandblasting operation should avoid sporadic operations, but the spraying area should not be too large at one time, and the time interval between the coating or thermal spraying process and the surface pretreatment process should be considered.
 Use hand or power tools to remove rust on the parts that cannot be sprayed by the spray gun.

6. Quality Control

 After the sandblasting is completed, the sandblasting and rust removal parts should be comprehensively inspected first, and then the cleanliness and roughness of the base steel surface should be inspected. Key Points should be checked for parts that are not easy to spray, and the requirements for rust removal by hand or power tools can be appropriately reduced. When inspecting the surface of the base steel for cleanliness and roughness, it is strictly forbidden to touch it;
 After sandblasting and rust removal, the cleanliness of the metal structure surface should reach Sa21/2, and should be compared with the photos provided in "Steel Surface Rust Grade and Rust Removal Grade before Coating", at least one comparison point every 2m2.
After sandblasting and rust removal, the surface roughness of the metal structure should reach Ry60 ~ 100μm. According to the technical requirements, take the corresponding roughness sample and compare it with a magnifying glass of at least 7 times. There is at least one comparison point every 2m2. When directly measuring with a surface roughness meter, there should be at least one evaluation point for every 2m2 surface, take the evaluation length as 40mm, measure 5 points within this length, and take the arithmetic mean of the surface roughness value for this evaluation point.